#import <UIKit/UIKit.h>@interface FirstViewController : UIViewController@end

#import "FirstViewController.h"#import "SecondViewController.h"@interface FirstViewController ()<SecondViewControllerDelegate>/** 用于寫入數據，最后該數據用于傳遞給第二個界面 */@property (weak, nonatomic) IBOutlet UITextField *first2Second;/** 用于顯示第二個界面返回來時傳遞的數據 */@property (weak, nonatomic) IBOutlet UITextField *displayWithSecond;@end@implementation FirstViewController- (void)viewDidLoad {  [super viewDidLoad];}#pragma mark - Navigation//點擊傳遞按鈕時會自動調用此方法- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {  SecondViewController *vc = (SecondViewController *)segue.destinationViewController;  if (self.first2Second.text.length > 0) {    //將該界面中的數據傳遞給第二個界面    vc.name = self.first2Second.text;  }  //設置當前控制器為SecondViewController控制器的代理  vc.delegate = self;}#pragma mark - 實現SecondViewControllerDelegate中的協議方法-(void)secondViewControllerDidDit:(SecondViewController *)viewController andName:(NSString *)name{  //將第二個界面中的數據返回給第一個界面（此界面）  self.displayWithSecond.text = name;}@end

#import <UIKit/UIKit.h>@class SecondViewController;@protocol SecondViewControllerDelegate <NSObject>/** SecondViewControllerDelegate協議中的方法 */-(void)secondViewControllerDidDit:(SecondViewController *)viewController andName:(NSString *)name;@end@interface SecondViewController : UIViewController@property(nonatomic,strong) NSString *name;@property(nonatomic,weak) id<SecondViewControllerDelegate> delegate;@end

#import "SecondViewController.h"@interface SecondViewController ()/** 用于寫入數據，最后將數據返回給第一個界面 */@property (weak, nonatomic) IBOutlet UITextField *second2First;/** 用于顯示第一個界面傳過來的數據 */@property (weak, nonatomic) IBOutlet UITextField *displayWithFirst;/** 點擊此按鈕，第二個控制器將彈出棧，界面將返回到第一個界面 */- (IBAction)second2First:(UIButton *)sender;@end@implementation SecondViewController- (void)viewDidLoad {  [super viewDidLoad];  //顯示第一個界面傳遞過來的數據信息  self.displayWithFirst.text = self.name;}//點擊該按鈕，數據將返回給第一個界面顯示- (IBAction)second2First:(UIButton *)sender {  if (self.second2First.text.length > 0) {    //如果有實現該協議方法的控制器，則將數據傳給該控制器    if ([self.delegate respondsToSelector:@selector(secondViewControllerDidDit:andName:)]) {      [self.delegate secondViewControllerDidDit:self andName:self.second2First.text];    }  }  [self.navigationController popViewControllerAnimated:YES];}@end